Reversible energy absorption of elasto-plastic auxetic, hexagonal, and AuxHex structures fabricated by FDM 4D printing

The present study aims at introducing reconfigurable mechanical metamaterials by utilising four-dimensional (4D) printing process for recoverable energy dissipation and absorption applications with shape memory effects. The architected mechanical metamaterials are designed as a repeating arrangement of re-entrant auxetic, hexagonal, and AuxHex unit-cells and manufactured using 3D printing fused deposition modelling process. The AuxHex cellular structure is composed of auxetic re-entrant and hexagonal components. Architected cellular metamaterials are developed based on a comprehension of the elasto-plastic features of shape memory polylactic acid materials and cold programming deduced from theory and experiments. Computational models based on ABAQUS/Standard are used to simulate the mechanical properties of the 4D-printed mechanical metamaterials under quasi-static uniaxial compression loading, and the results are validated by experimental data. Research trials show that metamaterial with re-entrant auxetic unit-cells has better energy absorption capability compared to the other structures studied in this paper, mainly because of the unique deformation mechanisms of unit-cells. It is shown that mechanical metamaterials with elasto-plastic behaviors exhibit mechanical hysteresis and energy dissipation when undergoing a loading-unloading cycle. It is experimentally revealed that the residual plastic strain and dissipation processes induced by cold programming are completely reversible through simple heating. The results and concepts presented in this work can potentially be useful towards 4D printing reconfigurable cellular structures for reversible energy absorption and dissipation engineering applications

Bio-inspired design, modeling, and 3D printing of lattice-based scale model scooter decks

This research aims at enhancing the performance of scale-model scooter decks by investigating various architected cellular metamaterial and bio-inspired core structure designs, such as honeycomb, tetrachiral, re-entrant, arrowhead, and star-shaped arrangements. An initial effort is made toward the design and rapid prototyping of small-scale deck with a uniform honeycomb core structure. More specifically, polylactic acid is utilized to fabricate complex structures via fused filament fabrication technique. Investigation is then focused on its mechanical performance, such as its bending properties obtained through a three-point bending test. Simulations are also conducted with different core configurations using a geometrically non-linear finite element method which is implemented. Experiments are carried out to verify the numerical results. After validation, various patterns are modeled, and eventually, it is observed that the functionally graded arrowhead structure has the best bending resistance, compared to other bio-inspired and mechanical metamaterial structures. At a constant force of 845 N, the functionally graded arrowhead design lowers the deflection in the middle of the scale model of scooter deck by up to 14.7%, compared to the uniform arrowhead structure. Furthermore, comparing the tetrachiral and functionally graded arrowhead configurations at a constant force, a 30% reduction in central deflection was observed. Due to the lack of similar results and designs in the specialized literature, this work could potentially advance the state-of-the-art scooter core designs and provide designers with architectures that could enhance the performance and safety of scooters

Huella de carbono en la producción de aceite de oliva de una empresa de San Juan

El cambio climático y sus consecuencias están ligados al desarrollo empresarial. Estoconlleva a buscar soluciones que atenúen el impacto de los procesos productivos en elmedioambiente. Pare esto es necesario poder medir la magnitud del impacto que unaempresa genera sobre el medio ambiente y sus componentes.Una de las herramientas de contabilidad y reporte ambiental es el cálculo de la Huella deCarbono (HC). En este trabajo se determinó la HC en la producción de aceite de oliva deuna empresa en la Provincia de San Juan, Argentina.Como paso inicial se definió el límite o alcance organizacional cuyas emisiones fueroncontabilizadas. La metodología de cálculo utilizada fue la que establece el GreenhouseGas Protocol (GHG), que es de libre acceso (www.ghgprotocol.org). Esta metodologíaclasifica las fuentes de emisión en 3 alcances (scopes): el primero corresponde a lasemisiones directas asociadas al consumo de combustible (gas oil y nafta) del tractor,montacargas y motosierra. El segundo comprende las emisiones de la electricidadconsumida por la maquinaria que se utiliza en planta; y el tercero comprende todas lasotras emisiones indirectas que son consecuencia de las actividades de la empresa comolas vinculadas a los proveedores de materias primas y el uso y fin de vida de losproductos generados y a todos los demás recursos como materiales, transporte, espacioocupado, bienes de equipo, entre otros que en el presente cálculo se excluyen.Es así que resulta la HC siendo de 3650 tCO2e, donde el 90% proviene del consumo degas oil; correspondiente a la producción de aceite de oliva en el año calendario 2012,con una producción promedio de 200 toneladas

Metamaterial boat fenders with supreme shape recovery and energy absorption/dissipation via FFF 4D printing

In maritime transportation, a fender acts like a bumper to absorb the kinetic energy of a boat berthing against a jetty, pier wall, or other boats. They have high energy absorption and low reaction forces, preventing damage to boats and berthing structures. The aim of this paper is to introduce a novel conceptual design for a new class of lightweight boat-fendering systems with superior energy absorption/dissipation and shape recovery features. Different metamaterials with honeycomb, re-entrant, and re-entrant chiral auxetic patterns are designed in the form of boat fender panels, and their thermo-mechanical behaviors are analyzed experimentally and numerically. A finite element modeling (FEM) is developed to investigate the compressive behaviors of boat fenders. Some of designs are 4D printed by fused filament fabrication of shape memory polylactic acid polymers and then tested thermo-mechanically. A good correlation is observed between numerical and experimental results, supporting the FEM accuracy. Results reveal that proposed boat fenders have considerable energy absorption/dissipation along with the capability to fully recover plastic deformations by simply heating up. The excellent mechanical property recovery of the proposed boat-fendering system is also shown under cycling loadings. Due to the absence of similar conceptual designs, models, and results in the specialized literature, this paper is expected to be instrumental towards 4D printing novel boat fenders with supreme energy absorption/dissipation and shape recovery properties promoting sustainability

Direct 3D printing of a two-part silicone resin to fabricate highly stretchable structures

The direct ink writing (DIW) method of 3D-printing liquid resins has shown promising results in various applications such as flexible electronics, medical devices, and soft robots. A cost-effective extrusion system for a two-part high-viscous resin is developed in this article to fabricate soft and immensely stretchable structures. A static mixer capable of evenly mixing two viscous resins in an extremely low flow regime is designed based on the required mixing performance through a series of biphasic computational fluid dynamics analyses. The printing parameters of the extrusion system are determined empirically, and the mechanical properties of the printed samples are compared to their molded counterparts. Furthermore, some potential applications of the system in soft robotics and medical training are demonstrated. This research provides a clear guide for utilizing DIW to 3D print highly stretchable structures

“Huella de carbono en la producción de vinos a granel y embotellados de una bodega de San Juan”

El calentamiento global de la atmósfera es un problema ambiental a escala mundial y es causado por el aumento de las concentraciones atmosféricas de los principales Gasesde Efecto Invernadero (GEI) que generan el efecto invernadero. Este es un proceso natural por el cual los GEI que están presentes en la atmósfera “atrapan” parte de laradiación que llega a la Tierra logrando amortiguar las oscilaciones térmicas entre día y noche, y crean condiciones ambientales que permiten un equilibrio en el ecosistematerrestre. El problema surge cuando las actividades antrópicas generan un incremento sustancial de los GEI que atrapan cantidades crecientes de radiación y produce unaumento de la temperatura promedio de la tierra, proceso denominado calentamiento global. La solución a este problema tiene dos dimensiones: la responsabilidad desde las políticas públicas y desde las políticas privadas. Desde lo público las Naciones Unidas afrontan el problema a través de la Convención Marco de las Naciones Unidas sobre elCambio Climático (UNFCCC) y/o la UNESCO con su Programa Hombre y Biosfera (MAB) y los países adhieren a estas políticas. Desde el ámbito privado las empresasdeben reconocer su impacto sobre el medio ambiente, medir la magnitud del mismo y decidir las políticas de producción más limpia mediante su mitigación y/o compensación(implica que se hacen cargo de sus externalidades). El objetivo de este trabajo es calcular la Huella de Carbono (HC) de la cadena de valor de la producción de vinosembotellados y a granel de la BODEGA FRANALCO y proponer medidas de mitigación y/o compensación. La metodologí a utilizada es la contabilidad y el reporte de GEIdefinidos por el GHG Protocol. Los resultados son: la empresa produce y vende 1,8 millones de litros, envasa 800.000 litros y envía a granel 1 millón de litros. El total deproducción de vino genera 1.564.545 kg de CO2. El promedio bruto por litro de vino es de 0.87 kg de CO2 por litro. Al desagregar en los dos diferentes tipos de envíos seobserva que los vinos envasados puestos en los mercados de destino explican 1.029.630 kg de CO2, que corresponde al 65.8 % del total de CO2 (y al 44.5% del totalde vino producido). Para cada litro de vino envasado se genera 1.37 kg de CO2 y por botella de 0,75 lts se genera 1.03 kg de CO2. Los vinos a granel generan por litro 0.534kg de CO2 puestos en destino y en total 534.514 kg de CO2. Las emisiones generadas son: carga y distribución el 53% de las emisiones, la etapa de producción del vino aportael 23% de las emisiones (explicado principalmente por el uso de energía eléctrica en el proceso), la etapa de fraccionamiento genera el 16% de las emisiones, donde elcomponente más importante son las botellas. Los valores obtenidos son similares a los valores de otros países. Por ALCANCE 1 corresponde el 21%, el ALCANCE 2 el30% y el ALCANCE 3 el 49%

Parrot beak‐inspired metamaterials with friction and interlocking mechanisms 3D/4D printed in micro and macro scales for supreme energy absorption/dissipation

Energy absorption and dissipation features of mechanical metamaterials have widespread applications in everyday life, ranging from absorbing shock impacts to mechanical vibrations. This article proposes novel bioinspired friction-based mechanical metamaterials with a zero Poisson's ratio behavior inspired from parrot's beaks and manufactured additively. The mechanical performances of the corresponding metamaterials are studied at both macro and micro scales by experiments and finite element analysis (FEA). An excellent agreement is observed between the FEA and both microscopic and macroscopic scale experiments, showing the accuracy of the developed digital tool. Performances are compared to traditional triangular lattice metamaterials. Both experimental tests and FEA results demonstrate the following advantages: 1) absorbing and dissipating energy per unit of mass (SEA) at large compressive strains without global buckling; 2) bistable deformation patterns including friction-based and interlocking mechanisms; 3) reversible deformation patterns after unloading; 4) shape recovery behavior after a heating–cooling process; and 5) the higher elastic modulus of micro metamaterials compared with their macro counterparts. This is the first demonstration of a bioinspired friction-based design of 3D-printed mechanical metamaterials that feature absorbing/dissipating energy, stability, and reversibility properties to cater to a wide range of sustainable meta-cylinders in micro and macro scales

Growth and characterization of TGS single crystal doped with NiSO₄ grown by Sankaranarayanan-Ramasamy method

234-238Unidirectional NiSO4 doped triglycine sulphate (TGS) single crystal of 15 mm in diameter and 150 mm in length was successfully grown in aqueous solution by Sankaranarayanan-Ramasamy (S-R) method. The characterization of the grown crystal was made by powder X-ray diffraction, UV-Vis. spectroscopy, Fourier transform infrared spectroscopy (FTIR), Vicker’s microhardness studies. The X-ray diffraction analysis revealed a monoclinic structure for the grown crystal. UV–Vis. analysis showed high transmittance for the doped TGS crystal in the entire visible region. FTIR spectrum verified the presence of various functional groups in the grown specimen. Vicker's microhardness studies of the doped TGS crystal showed that it is harder than pure TGS crystal. The density of the doped crystal was found to be higher than that of the undoped one

Progress and improvement of the manufacturing process of snake antivenom

Antivenoms have been used successfully for more than a century and up to now constitute the only effectivetreatment for snakebites .The production of antivenin started long time ago when the calmette was preparedthe antivenom in 1894.The method currently used to prepare antivenom by most of the manufacturers areoriginated from the method of Pope which was develop in 1938. Several new approaches in the production ofantivenom have been proposed to produce IgG, F(ab)2, F(ab) antivenin to improve their quality .Theseimprovement include complete or partial modification in the antivenom production regarding animal,immunization protocols , new adjuvants in hyperimmunization of animals , purification processes ( caprylicacid ,chromatography , diafiltration and ulterafiltration ),enzymatic digestion of IgG (pepsin, papain ) andfractionation of venom .When the IgG is digested enzymatically, different fragments are obtained depending on the enzyme used, that is, if papain is used, three fragments are obtained, the crystallizing fragment (Fc) and two antigen-binding fragments F(ab) and, if pepsin is used, one F(ab')2 fragment is obtained, while thecrystallizing fragment is digested. Fab and F(ab)2 fragments conserve their capacity to specifically bind to the antigen that gave rise to them